1. Field of the Invention
The present invention relates to electronic apparatus with a direct-viewing type liquid crystal panel which uses a light emitting diode (LED) as an illumination source for the liquid crystal panel.
The electronic apparatus of the invention include information processing devices, such as note or laptop personal computers and mobile computers, head-mounted displays, video cameras, digital still cameras, car navigation systems, and cellular phones.
2. Description of Related Art
In recent years, research and development have been conducted on the liquid crystal panel production technology and resulted in a relatively inexpensive price of the liquid crystal panel. Further, as the information society has progressed in the filed of the Internet and electronic mail, the note type personal computers (hereinafter referred to as note type PCs) have rapidly prevailed.
The digital still cameras and video cameras incorporate a liquid crystal panel so that a photographed picture can be viewed on the site. Because of this advantage, these cameras have gained popularity with consumers.
There are two types of liquid crystal panel: a transmission type and a reflection type. The transmission type liquid crystal panel has a backlight installed at the back of the panel whose illumination light passes through the liquid crystal panel to form an image on the display that can be seen by the user. The reflection type liquid crystal panel, on the other hand, does not require a backlight and forms an image by reflecting external light by the liquid crystal panel. The display quality of the reflection type, however, does not match that of the transmission type.
Because the note PCs and digital cameras are used for displaying Internet home pages in color, importance is placed on the display quality such as color reproducibility and the liquid crystal panel for use with these electronic devices needs to be of a transmission type.
Generally, the backlight source for the transmission type liquid crystal panel uses a cold cathode tube that emits white rays. The cold cathode tube is a fluorescent lamp and thus requires a high-voltage AC power supply to be turned on. Hence, the electronic devices such as note PCs require a DC-AC converter for converting a DC power supply into an AC power supply of several hundred volt.
At present, essential factors in improving the portability of electronic devices are reductions in power consumption, size and weight. Although the power consumption of the liquid crystal panel itself is small, the use of a backlight of a conventional cold cathode tube requires a high voltage, which hinders the reduction in power consumption. Another drawback is that the cold cathode tube has a short life time of about 2,000 hours.